1. Field of the Invention
The present invention generally relates to automated inspection systems for identifying and sorting objects according to their geometrical and/or electromagnetic characteristics.
2. State of Art
It is well known that automated inspection systems can recognize geometric characteristics of parts based upon their interaction with fields of acoustic waves. In this regard, attention is drawn to U.S. Pat. Nos. 4,095,475; 4,200,921; 4,287,769; 4,557,386; and 4,576,286. Also, it is known that automated inspection systems can recognize electromagnetic characteristics of parts by employing electromagnetic fields which interact with the parts to provide "electromagnetic signatures".
In such inspection systems, two types of errors may arise: false acceptances and false rejections. False acceptance errors arise when parts are accepted which are defective or otherwise do not conform to predetermined standards. For example, in an automated inspection system for inspecting bolts, a false acceptance error would arise if the system accepted a bolt with a damaged head. Also, a false acceptance error would arise if a screw, although nondefective, were to pass an inspection which was intended to pass only bolts. False rejection errors would arise if the system rejected parts which were not defective but, in fact, conformed to predetermined standards. When automated inspection systems are used to sort parts, false rejection and false acceptance errors result in mixing different kinds of parts.
In automated inspection systems which recognize geometrical or electromagnetic characteristics of parts by their interactions with fields of waves, false rejection and false acceptance error often relate to the state in which parts are presented for inspection. For instance, if parts are presented for inspection in unusual positions, the probability increases that such systems will make inspection errors. Also, if parts are submitted for inspection while vibrating or wobbling, the probability increases that such systems will make inspection errors.